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Acorn Archimedes A400/1 Series

[A400]     [Archimedes]     [A540 ]  


Launched in May 1989 the A4x0/1 range were improved versions of the old A4x0 range. In particular they included the MEMC1a memory controller which gave a slight performance improvement over the older systems. The range consisted of the A410/1 with IMB RAM and a floppy disc drive, the A420/1 with 2MB RAM, a 20MB ST506 hard disc and floppy disc drive and the A440/1 with 4MB RAM a 50MB ST506 hard disc and a floppy disc drive.

The following models were produced [that I know of]:

Manuals and documents

Here are 2 Acorn A400/1 product brochures with details of the new range:
Acorn APP223 Archimedes A400/1Acorn A400/1 brochure

Here is the Archimedes Welcome Guide (for RISC OS 2) 

Here is the Acorn A400/1 & R140 Service Manual. 

A410/1 (No. 1)

The A410/1 had 1 MB memory, no hard disc and RISC OS 2.00 .

My A410/1 was my main computer from 1989 to 1994 until I bought a RiscPC. I think I bought it from Norwich Computer Services, because I remember driving over to collect from Bedford where I was living. When I bought it I traded in my A310 with twin floppy drives. the major upgrades were a memory upgrade to 4MB, 40MB hard disc, a VIDC Enhancer and an ARM3 CPU. I also bought an Iiyama monitor which was why I needed the VIDC Enhancer. Over the years I installed and removed quite a number of podules.

In 1990 I went to work in Singapore for 2 years and my A410/1 went with me, I think it was the first Archimedes in Singapore. It certainly confused many Singaporeans who even then were hooked on PCs
Here are some photographs:

[Still awaiting photos]

A410/1 (No.2)

This Acorn A410/1 has been upgraded from 1MB to 4MB RAM, with RISC OS 3.10, and a Beebug 5¼" floppy disc interface.

Acorn A410/1 running RISC OS 3

Acorn A410/1 running RISC OS 3 

This A410/1 has an external hard disc (on right), the hard disc is an ST-251. The monitor is an Acorn AKF12 with a Multiguard and glare screen and document holder..

Acorn A410/1 Desktop

Acorn A410/1 showing RISC OS 3 desktop 

The desktop shows the hard disc icon on the far left of the icon bar.

Acorn A410/1 right

Acorn A410/1 (right) 

Acorn A410/1 back

Acorn A410/1 (back) 

This picture shows the back of the A410/1 with the ports at the bottom and the podule expansion slots above. The blanking plate is missing for podule 2 and podule has a Beebug 5¼" floppy disc interface installed. The ports, from the left, are:

Acorn A410/1 bottom

 Acorn A410/1 (bottom)

This picture shows the bottom of the A410/1 with the label and serial number 27-AKB40-1000943, which suggests that this is an authentic, not modified, A410/1.

Acorn A410/1 open

Acorn A410/1 with top cover removed 

This picture shows the internals of the Acorn A410/1:

Acorn A410/1 with Beebug interface removed

 Acorn A410/1 with Beebug 5¼" floppy disc interface removed

Acorn A410/1 with backplane removed

Acorn A410/1 with backplane removed

Acorn A410/1 motherboard top 

Acorn A410/1 mother board (top)

This picture shows the Acorn A400/1 motherboard, the Acorn Universal board is used in all models. From left to right and bottom to top the picture shows:

Here is a HiRes picture of the A410/1 motherboard .

Acorn A410/1 motherboard bottom 

Acorn A410/1 motherboard (bottom) 


Serial No.27-ABK40-100046427-AKB40-1000943
Unique Indentityn/an/a
Motherboard part no.Acorn Universal Brd
283,000 Issue 2
Acorn Universal Brd
283,000 Issue 2
Motherboard serial no.PC-189-0591PC- -1260
CPU ModelAleph1 ARM3VLSI VL2333-QC
CPU Clock25MHz8MHz
Memory ControllerMEMC1aMEMC1a
Memory Clock8MHz8MHz
Video ControllerVIDC1aVIDC1a
Floppy Disc DriveCitizen OSDC-65ACitizen OSDC-65A
Hard Disc ControllerST506/MFMST506/MFM
Hard Disc Drive40MB
NEC D3142
External ST-251
Backplane ModelAcorn A410, 440, 680
serial no. 180703
Acorn A410.440, 680
serial no. 239810
Backplane part no.0283,040 Issue 30283,040 Issue 3
Podule 0Computer Concepts Scan Junior
Serial no. 4577
Podule 1 Clares Sound Samplern/a
Podule 2Lingenuity Snapshotn/a
Podule 3n/aBeebug 5¼" floppy
disc interface
Other upgradesAtomwide VIDC Enhancernone
OS Date30-Apr-9230-Apr-92
SICK v1.22
ARMSi v4.0

A420/1 (No. 1)

The A420/1 was launched at the same time as the A420/1 in July 1989. It differed only in having 2MB RAM installed instead of 1MB on the A410/1 and had a 20MB ST506 hard disc.

I bought these 2 A420/1s in 2004, one had been deliberately damaged (I think they were rescue computers) with many of the ICs and motherboard smashed up with a screwdriver or similar tool. I rebuilt it, it's the AKB44, but it is a bit of a mongrel.

The first A420/1 is an AKB46, which is the product code for an A440/1 Learning Curve. However it has 2 MB memory, no ST506 hard disc and A420/1 on the front. I have added a Watford Electronics 25MHz ARM3 Upgrade,  Pinapple DigitiserVTi SCSI and user port podule and an Atomwide Ethernet III podule which is not really useable with only 2MB RAM, especially with the Universal Boot installed.
Here are some pictures:

  A420/1 running RISC OS 3.10

A420/1 running RISC OS 3.10

 A420/1 logo 

A420/1 logo

 The Archimedes A420/1 logo on the front of the computer. But it does not match the Serial number on the base...

  A420/1 Serial No.

A420/1 serial no.

 The Archimedes serial number (25-AKB46-1001228) on the baottom of the computer. But the AKB46 is a A440/1 Learning Curve model

  A420/1 rear view

A420/1 rear view

 The back of the A420/1 showing the Atomwide Ethernet III podule in the top left. The VTi SCSI/User port podule is next to it in the top center. The Pineapple Digitiser is in the middle below the 2 previous podules. At the bottom are the A420/1 ports - 75Ohm Hi-Res Monitor (2 x BNC), Analogue RGB, Serial, Headphones and Parallel Printer. The Econet Interface is not fitted. The power supply and On/Off switch are on the right.

  A420/1 with top off

A420/1 with the cover off

 This shows the power supply on the right with the fan and batteries for the CMOS RAM in fornt of it. The red VTi SCSI/User port podule in the middle connected, by the ribbon cable to the SCS Drive. The Atomwide Ethernet II podule in hte top right with the floppy drive below it.

  A420/1 motherboard

A420/1 motherboard

 The A420/1 motherboard, the front is on the left. On the left bottom is the keyboard connector with the RAM behind it, you can see that only the back row is populated, the front row are sockets which can be used to upgrade to 4MB. The IFEL ARM3 upgrade is to the right of the RAM with the MEMC1a above it. The connectors to the right of the MEMC1a are for the floppy drive and ST506 hard drive. In the middle at the bottom is the connector for the backplane with the RISC OS ROMs to the right. The VIDC is the square IC to the right of the 4 RISC OS ROMs.

A420/1 (No. 2)

 The second A420/1 is the AKB44, which is an A440/1, but the label on the front says A420/1! Since I had to get a new motherboard (curtesy of IFEL) and added the Aleph1 30MHz ARM3 from elsewhere, I suspect it is more an A4x0/1 than anything else. It is also a very basic system with no podules and no hard drive.
Here are some pictures:

 Acorn A420/1


 A420/1 motherboard

A420/1 open

The A420/1 with the top removed, showing the floppy drive on the bottom right with the gold label of the Aleph1 30MHz ARM3 CPU above it. There is no hard drive fitted.


Serial No.27-ABK44-100009527-ABK46-1001228
Unique Indentityn/an/a
Motherboard part no.Acorn Univrsal Brd
0283,000 issue 2
Acorn Universal Brd
0283,000 issue 3
Motherboard serial no.PD-299-0183PC-409-6308
CPU ModelAleph1 ARM3
Watford Electromics ARM3
CPU Clock30MHz25MHz
Memory ControllerMEMC1aMEMC1a
Memory Clock8MHz8MHz
Video ControlerVIDC1aVIDC1a
Floppy Disc DriveCitizen OSDC-65CCitizen OSDC-65C
Hard Disc Controlleron-board ST506/MFMon-board ST506/MFM
Hard Disc Driven/a 200MB
Backplane ModelA410, A440, A680 BackplaneA410, A440, A680 Backplane 
Backplane part no.0283,040 Issue 30283,040 issue 3
Podule 0n/aAtomwide Ethernet III BNC
Podule 1n/a VTi User port/SCSI podule
Issue 1
Podule 2n/aPinapple Colour Digitiser
Podule 3n/an/a
Other upgrades  
OS Date30-Apr-9230-Apr-92
SICK v1.22
ARMSi v4.0


The third model Acorn launched in July 1989 was the A440/1. It not only had 4MB RAM, but also a 53MB ST506 hard disc.

I bought this A440/1 in 2006. It is also a bit of an anomaly because although it says A440/1 on the front (see pictures below, the serial number on the bottom gives the product code ad AKB40 which is an A410/1! However the Computer has 4MB RAM and a 20MB Seagate ST125 MFM hard disc. It had one owner from new and was supplied by Watford Electronics. I think that Watford Electronics must have taken an A410/1 and upgraded it to the A440/1 specification. It has subsequently been upgraded to RISC OS 3.10 but still has its ARM2. The ST125 hard disc no longer works, an Oak Solutions Worra Winne 80MB hard disc and Oak SCSI card have been added to replace it.
Here are some pictures of the A440/1:

A440 with Oak Worra Winnie  

Acorn 440/1 with Oak Worra Winne on left

Acorn A440/1 with Oak solutions Worra Winnie 80MB SCSI hard disc and an AKF12 monitor . The stickers on the system box and the monitor show that it was originally supplied by Watford Electronics. There is a Multiguard Professional anti-glare screen on the monitor.  

  A440/1 System Unit front

Acorn 440/1 system unit (front)

 The Archimedes label says Archimedes A440/1, unfortunately it conflicts with the AKB40 product code in the serial number! 

  A440/1 bottom

Acorn A440/1 showing serial number (bottom)

The bottom of the system unit with the serial number 27-AKB40-1007658, which is an A410/1 serial number! So either the case has been swopped at some point or the Archimedes was upgraded from an A410/1 to an A440/1.  

 A440/1 back 

Acorn A440/1 from back

 The back of the A440/1 showing, from left to right and top downwards: the Oak Solutions SCSI podule and connector, Power In & Out and On/Off switch, 75Ohm Hi-Res Monitor (2 x BNC), Analogue RGB, Serial, Headphones and Parallel Printer. The Econet Interface is not fitted. Over the top you can see the podule backplane. 

  A440/1 label 

Archimedes A440/1 label

 Label on the front of the system unit shows it to be an A440/1, also shows it was sold by Watford Electronics. But the serial number says it is an A410/1. Why, well I think Watford Electronics upgraded it and changed the label on the front. I still have a number of spare labels that came with an upgrade to my original Archimedes. 

  A440/1 open

Acorn A440/1 with top cover open

  The A440/1 with the top removed showing the floppy and hard disc at the front, with the top of the backplane behind and the power supply on the left. 

A440/1 with front panel removed  

Acorn A440/1 with front off

 The Acorn A440/1 with the front removed, showing from left to right and front to back: the cooling fan, the batteries for the CMOS RAM, the Seagate ST-125 MFM hard disc, the floppy disc drive, the power supply (behind the cooling fan), the backplane (behind the disc drives and the poorts at the back of the case. 

 A440/1 with discs removed 

Acorn A440/1 with discs removed

 The Acorn A440/1 with the hard disc and floppy disc drive removed, showing: the RAM under the disc bridge, the keyboard socket in the front right, the ARM2 CPU, behind the disc bridge, with the orange spot on it, the MEMC1a to the left of the CPU. 

  A440/1 showing RAM

Acorn A440/1 showing RAM

 The Acorn A440/1 without the backplane looking along the motherboard. The point to notice is that some of the RAM chips are socketed, which suggests they have been installed as part of an upgrade.

 A440/1 motherboard 

 Acorn A440/1 motherboard

The Acorn A440/1 motherboard. A Hi-Res version of this picture is available HERE  .  


Serial No. 27-AKB40-1007658
Unique Identityn/a
Motherboard Part No. Acorn Universal Brd
0283,000 issue 3
Motherboard Serial no.PC-389-5417
CPU ModelVL2333-QC
CPU Clock8MHz
Memory ControllerMEMC1a
Memory Clock8MHz
Video ControllerVIDC1a
Floppy Disc driveCitizen OSDC-65C
Hard Disc ControllerST506 MFM
Hard Disc DriveSeagate ST125
Backplane ModelA410, A440, A680 Backplane 
Backplane part no. 0283,040 issue 3
Oak Solutions 16bit SCSI
OS Date15 Sep 88